Several different integrated circuit technologies are available to circuit and system designers in which to realize their designs. These technologies include for example, bipolar, complementary metal oxide semiconductor (CMOS), bipolar-CMOS (Bi-CMOS), gallium arsenide (GaAs), and others. As would be expected, integrated circuits based on different technologies, or based on differing logic families within a technology, are often required to operate within a single system, and hence, must accurately communicate one with another.
One common problem that must be dealt with is the differing logic level voltages associated with the differing technologies, or between differing circuit families within a single technology. This problem is sometimes further exacerbated by supply voltage levels which may vary significantly, not only between different technologies, but even amongst circuits of like technologies. Additionally, it is now common to have a higher voltage to operate input/output circuits and a second lower voltage to operate internal circuits. In order to deal with such differences between circuits and technologies, designers rely upon input buffer circuits (also known as "voltage translators", or "differential receivers") that are capable of translating input signal levels from an external circuit into needed logic levels of internal circuits.
An input buffer circuit with a hysteresis characteristic has been used in order to prevent a situation where the input buffer circuit turns on or off by not only the input signal but also by noise associated with the input signal, thereby inhibiting the proper propagation of the input signal. The input buffer circuit with a hysteresis characteristic has two threshold values, namely V.sub.Th and V.sub.Tl. V.sub.Th is the threshold value for the case where the input signal rises, and V.sub.Tl is the threshold value for the case where the input signal falls. Accordingly, if the input signal becomes larger than V.sub.Th and the input buffer turns on, the circuit will not go low until the input voltage becomes smaller than V.sub.Tl. In this situation, noise with a width of V.sub.Th -V.sub.Tl is eliminated.
Ideally, the hysteresis characteristic is centered about a reference voltage of the input buffer circuit. However, power supply variations and component tolerances often result in a distorted hysteresis characteristic, e.g., non-symmetrical about the reference signal. Thus, there exists a need in the art for an input buffer circuit or differential receiver designed with a hysteresis characteristic that is capable of being held more closely centered about the reference signal.